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Title: Corrosion-induced gas generation in a nuclear waste repository: Reactive geochemistry and multiphase flow effect

Corrosion of steel canisters, stored in a repository for spent fuel and high-level nuclear wastes, leads to the generation and accumulation of hydrogen gas in the backfilled emplacement tunnels, which may significantly affect long-term repository safety. Previous studies used H{sub 2} generation rates based on the volume of the waste or canister material and the stoichiometry of the corrosion reaction. However, iron corrosion and H{sub 2} generation rates vary with time, depending on factors such as amount of iron, water availability, water contact area, and aqueous and solid chemistry. To account for these factors and feedback mechanisms, we developed a chemistry model related to iron corrosion, coupled with two-phase (liquid and gas) flow phenomena that are driven by gas-pressure buildup associated with H{sub 2} generation and water consumption. Results indicate that by dynamically calculating H{sub 2} generation rates based on a simple model of corrosion chemistry, and by coupling this corrosion reaction with two-phase flow processes, the degree and extent of gas pressure buildup could be much smaller compared to a model that neglects the coupling between flow and reactive transport mechanisms. By considering the feedback of corrosion chemistry, the gas pressure increases initially at the canister, but later decreasesmore » and eventually returns to a stabilized pressure that is slightly higher than the background pressure. The current study focuses on corrosion under anaerobic conditions for which the coupled hydrogeochemical model was used to examine the role of selected physical parameters on the H{sub 2} gas generation and corresponding pressure buildup in a nuclear waste repository. The developed model can be applied to evaluate the effect of water and mineral chemistry of the buffer and host rock on the corrosion reaction for future site-specific studies.« less
Authors:
; ;
Publication Date:
OSTI Identifier:
953233
Report Number(s):
LBNL-1800E
Journal ID: ISSN 0883-2927; APPGEY; TRN: US0902726
DOE Contract Number:
DE-AC02-05CH11231
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Geochemistry; Journal Volume: 23; Related Information: Journal Publication Date: 2008
Research Org:
Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (US)
Sponsoring Org:
Earth Sciences Division
Country of Publication:
United States
Language:
English
Subject:
54; 58; ANAEROBIC CONDITIONS; BUILDUP; CHEMISTRY; CONTAINERS; CORROSION; FEEDBACK; GEOCHEMISTRY; HYDROGEN; IRON; MULTIPHASE FLOW; POSITIONING; RADIOACTIVE WASTES; SAFETY; SPENT FUELS; STEELS; STOICHIOMETRY; TWO-PHASE FLOW; WASTES; WATER